Alloy



Watented June 18, 1935 AILMUHY James M. Lohr,

Driver-Harris @ompany, poration or New .llersey Morristown, N. 3., assignor to Harrison, N. it, a cor- No Drawing. Application October 12, 1934, Serial No. 748,083

5 oxidation at high temperatures is essential. The

alloys forming the subject matter of my invention are characterized by the ability to resist oxidation and by a prolonged life, exceeding that of other known alloys, when used under high temperature conditions.

While nickel-chromium and nickel-chromiumiron alloys having the ability to resist oxidation at high temperatures are known, their period of usefulness at high temperatures is often not as long as desired. I have found that the addition of small quantities of molybdenum, zirconium and calcium to such nickel-chromium alloys increases their period of useful life at high temperatures to a remarkable degree. The alloys forming the subject matter of the present application may also contain small quantities of either silicon or manganese or both of these elements.

In carrying out my invention 1' add small quantities of molybdenum, zirconium and calcium, with or without silicon or manganese t0 nickel-chromium or nickel-chromium-iron alloys. The nickel-chromium alloy most generally used in the art consists of 80 parts of nickel and 20 parts of chromium and I find it advantageous to add the other metals mentioned above to nickelchromium alloys of substantially these proportions. Slight variations in the proportions of nickel and chromium may be made, without departing from the spirit of my invention. Thus the chromium content may be from 15 to 25 percent and the balance nickel.

Likewise the most generally used proportions of nickel, chromium and iron in nickel-chromium-iron alloys is percent nickel, 10 to 15 percent chromium and the balance iron and I find it advantageous to employ substantially these proportions of those ingredients. These proportions may also be varied, the nickel, however, forming the major portion of the alloy, and the nickel-chromium content being such that the alloy will have the characteristics of a nonferrous alloy. In preparing alloys containing the additional elements enumerated, the quantities of the additional elements are subtracted from the nickel content, as for example, when molybdenum, zirconium and calcium are added to an alloy containing 15 to 25 percent chromium and the balance nickel, the final alloy will contain 15 to 25 percent chromium, molybdenum, birconium and calcium in the percentages herein stated and the balance nickel.

The proportions of molybdenum, zirconium and calcium may vary Within certain limits. I have found that the best results are obtained when these metals are present in the nickelchromium or nickel-chromium-iron alloy within the following limits:

Percent Molybdenum 1.0 to 20.0 Zirconium 0.1 to 1.0 Calcium 0.01 to 0.20

If manganese or silicon are employed, they may be used within the following limits:

Percent Manganese 0.02 to 2.0 Si1ic0n 0.20 to 2.0

The preferred proportions of the alloying agents are as follows:

Percent Molybdenum 2 to 10 Zirconium 0.1 to 0.3 Calcium 0.02 to 0.05 Manganese 0.05 to 1.0 Silicon 0.40 to 1.0

The molybdenum may be added as the pure material if alloys completely free from iron are desired. If this freedom from iron is not essential, the addition may be made by means of ferro molybdenum containing substantially of molybdenum. The zirconium may be added as nickel zirconium containing 25 to 30 percent of zirconium. The calcium may be added as metallic calcium.

Nickel-chromium and nickel-chromium-iron alloys containing the above ingredients within the proportions given have been found by tests to have a greatly increased period of useful life when exposed to high temperatures. For the purpose of determining the life of such alloys at high temperatures I have tested them by the method of 7 test outlined in Tentative accelerated life test for metallic materials for electrical heating-of the American Society For Testing Materials described in vol. 29 of the Proceedings of the Thirty- Second Annual Meeting of the American Society for Testing Materials beginning on page 613. The method is substantially as follows:

A sample of the wire to be tested, free from kinks, approximately twelve inches long and of about .025" diameter, is mounted vertically on the test board, the upper end being held in position by means of a suitable binding post. A 10 gram weight is attached to the lower end of the specimen. A short piece of wire is attached to the 10 gram weight and projects downward into a cup of mercury where it may move freely up and down. A rheostat and an interrupter are.connected in series with the specimen to the power supply. The test is run on constant temperature at a standard temperature chosen for the alloy under consideration for the first twenty-four hours. Thereafter itis run on constant voltage to the burnout. The life in hours up to a 10 percent increase in resistance is known as useful-life while the life to the burnout is known as total life. Throughout the test the power is on two minutes and oil. two minutes. This is accomplished by means of an interrupter.

In testing the alloys of my invention according to the above described method a reference sample composed of percent nickel and 20 percent chromium and no alloy additions having an approximate life of hours was used. This value is considered as percent and the useful life of the samples tested is determined in corresponding percentage values.

The results obtained with nickel-chromium alloys containing molybdenum, zirconium, and calcium are given below:

An alloy of 80 percent nickel and 20 percent chromium to which molybdenum, zirconium and calcium had been added was found on analysis to contain:

V Percent Molybdenum 5.21 Zirconium 0.19

Calcium 0.02

This alloy developed on life test a useful life of 1185%.

Another alloy of 80 percent nickel and 20 percent chromium to which the same three materials had been added was found on analysis to contain:

Percent Molybdenum 4.83 Zirconium 0.15 Calcium 0.01

Percent Molybdenum 4.83 Zirconium 0.15 Calcium 0.01 Silicon 0.51 Manganese 1.04

In the claims the phrase nickel-chromium alloys is meant to include alloys of nickel and chromiumand is also intended to include alloys formed from nickel, chromium and iron.

In the alloys referred to herein, small amounts of phosphorous and sulphur may be present as impurities. Likewise small quantities of iron may be'present in nickel-chromium alloys when the molybdenum is added as ferro-molybdenum, and small quantities of carbon may also be present. The nickel may also contain about .1 percent of cobalt.

I claim:

1. A nickel-chromium alloy containing 15 percent to 25 percent chromium, 1 to 20 percent molybdenum, 0.1 to 1.0 percent zirconium and 0.01 to 0.20 percent calcium balance nickel.

2. A nickel-chromium alloy containing 15 percent to 25 percent chromium, 2 to 10 percent molybdenum, 0.1 to 0.3 percent zirconium and 0.02 to 0.05 percent calcium balance nickel.

3. A nickel-chromium alloy containing substantially 20 percent chromium, substantially 5 percent molybdenum, substantially 0.2 percent zirconium, and substantially 0.02 percent calcium balance nickel.

JAMES M. LOHR. 

